Don't fade out active page outline during drag-and-drop

=> Keep page backgrounds stable and only slightly modify the alpha + add stroke for active page
=> Don't shrink cell outlines to be too small (issue in hotseat on some devices)
=> Reduce cell radius to 22dp

Bug: 185163323
Test: manual

Change-Id: Ic17999f5672a3355dceeb25af923f02e960389d9